fizzbuzz.hs

data FizzBuzz = FizzBuzz
              | JustInt Int
              | Fizz
              | Buzz

instance Show FizzBuzz where
    show FizzBuzz = "FizzBuzz"
    show Fizz = "Fizz"
    show Buzz = "Buzz"
    show (JustInt x) = show x

multipleOf x y = x `mod` y == 0

fizzbuzz :: [Int] -> [FizzBuzz]
fizzbuzz = map (_fizzbuzz . precalc)
  where
    _fizzbuzz :: (Int, Bool, Bool) -> FizzBuzz
    _fizzbuzz (_, True, False) = Fizz
    _fizzbuzz (_, False, True) = Buzz
    _fizzbuzz (_, True, True) = FizzBuzz
    _fizzbuzz (x, False, False) = JustInt x

    precalc :: Int -> (Int, Bool, Bool)
    precalc x = (x, x `multipleOf` 3, x `multipleOf` 5)

main = mapM_ (putStrLn . show) $ fizzbuzz [1..]